Renal cell carcinomas can show up on an ultrasound scan. Many times, they’re found when doctors are performing an imaging scan for another purpose.

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Renal cell carcinomas are the cause of about 90% of all kidney cancers. Doctors often detect them by accident when performing an ultrasound, CT scan, or MRI for another health reason.

If your doctor detects a mass on a kidney during an ultrasound, they’ll use additional testing to confirm a diagnosis of renal cell carcinoma and to stage the cancer.

This article takes a look at whether ultrasounds are an effective screening tool for renal cell carcinoma and how doctors diagnose and stage this type of cancer.

Researchers have looked at ultrasounds as a possible screening tool to find and treat cancers like renal cell carcinoma early — before they’ve metastasized to other areas of the body. Currently, about a quarter of all people with renal cell carcinoma already have evidence of metastasis when their cancer is first discovered.

While ultrasounds have the potential for screening, there are some limitations.

In one study, ultrasound was successful in detecting between 80–90% of renal cell carcinomas, but accuracy was dependent on the size of the tumor. Researchers found that ultrasounds could lead to false-negative results in tumors smaller than 3 cm (1.18 inch).

Ultrasounds may, however, be a useful screening tool for high risk individuals or to evaluate how effective treatments are.

Typically, the best way to detect renal cell carcinoma is with a CT scan that uses a contrast dye. About 50% of people with renal cell carcinoma don’t develop any symptoms, but the cancer is visible on a scan that they have for another reason.

Once a doctor discovers renal cell carcinoma, they’ll usually perform additional CT scans with or without contrast dye, and a biopsy may also be done to examine tissue samples at the microscopic level. After confirming a diagnosis, a doctor will then stage the cancer.

Staging of renal cell carcinoma

Staging is important because it provides information about metastasis. The stage of your cancer will help guide treatment strategies and allow your healthcare team to estimate a prognosis for recovery.

Stages of renal cell carcinoma are:

  • Stage 1: The tumor is confined to your kidney and measures 7 cm (centimeters) or smaller
  • Stage 2: The tumor is confined to your kidney and measures between 7 cm and 10 cm
  • Stage 3: The tumor extends to local areas outside of your kidney
  • Stage 4:The tumor or cancer cells have spread to more distant areas of your body, such as your adrenal glands

Half of all cases of renal carcinoma develop without noticeable symptoms. Doctors usually find it when an ultrasound or CT scan is done to investigate another issue.

If symptoms of renal cell carcinoma are present at the time of diagnosis, they can include things like:

Signs of more advanced renal carcinoma or kidney cancer can also include things like:

  • high blood pressure
  • leg swelling
  • weight loss
  • cough
  • bone pain

More noticeable symptoms are usually the result of metastasis, and about 25% of people’s cancer is in stage 3 or 4 when they receive a diagnosis of renal cell carcinoma.

Renal cell carcinoma doesn’t usually cause symptoms, and most cases are found during an ultrasound, CT scan, or MRI that’s being done for another reason.

Routine screening isn’t widely recommended for renal cancer, but improved ultrasound technology is making this tool a better option for screening people at high risk or who are already undergoing treatment.